The invention relates to compositions, e.g., personal wash perfume-containing compositions, which are able to deliver perfume benefits (i.e., xe2x80x9cburstxe2x80x9d or increase in perfume headspace relative to undiluted composition) upon dilution in water. More specifically, by being aware of which properties of the perfume and of the surfactant systems in which they are found are responsible for perfume release on dilution, applicants have been able to provide both specific compositions and processes for selecting perfumes and/or surfactant systems in said compositions which meet defined criteria (as defined, for example, in perfume burst index) and thereby provide aroma burst of at least defined levels upon dilution.
Perfume is a key component for a favorable consumer experience with home and personal care products. It is also often the most costly component of the formulation. Typically most of the fragrance is quickly lost as the product is used because most of the perfume is trapped in the surfactant system. There has been a long-standing need to improve the utilization of perfumes and to design compositions that provide maximum and prolonged impact in use. It is one objective of this invention to develop a means by which products can be developed to provide greater fragrance impact and novel fragrance characteristics in use.
To this end, the applicant has found that perfume activity (e.g., the aroma of the perfume) both in a product (e.g., surfactant containing product) and upon use (e.g., dilution of product in shower) can be correlated to the thermodynamic characteristics of (1) the perfume itself and (2) the formulation in which the perfume is found.
For example, the degree to which a perfume will partition into oil or water (measured by a so-called xe2x80x9cpartition coefficientxe2x80x9d and a reflection of the hydrophobicity of the perfume) and the degree to which the perfume evaporates (measured by xe2x80x9cvolatility constantxe2x80x9d and a reflection of the volatility of the perfume) are two significant characteristics of the perfume which strongly affect the potential perfume xe2x80x9cburstxe2x80x9d when said product is diluted. By burst is meant an increase in the concentration of perfume in the vapor phase above the solution (i.e., this is also known as perfume headspace) with respect to the undiluted product and composition. The vapor phase can of course vary depending on product, for example, from a small area above a bottle of perfume to an area in a shower stall.
As noted, the perfume burst is affected not only by the perfume properties, but also by properties of the formulation in which the perfume is found. Thus, the number and type of surfactant micelles found in a surfactant solution also has an effect. For example, in a surfactant with high critical micellization concentration (CMC) (in compositions of high CMC, micelles do not form as readily) perfume xe2x80x9cburstxe2x80x9d would occur more readily and less dilution is required. The critical micellization concentration is defined as the surfactant concentration at which micelles begin to form from unassociated surfactant monomers (M. J. Rosen, Surfactants and Interfacial Phenomena, 2nd Ed., 1989). Conversely, in a surfactant with low critical micelle concentration (e.g., one where micelles do form easily or, stated differently, don""t break apart as readily once formed), a perfume, being generally more hydrophobic, tends to stay in the surfactant more readily. As a result, the perfume will tend not to xe2x80x9cburstxe2x80x9d (increase perfume headspace) as readily and, to achieve more headspace, more dilution may be required.
Other important formulation factors which may affect the xe2x80x9cburstxe2x80x9d of the perfume may include, but are not limited to, perfume content in solution and surfactant to water ratio.
Still another factor which can affect perfume xe2x80x9cburstxe2x80x9d is the environment in which it is found, e.g., such environmental factors as (1) overall sample amount; (2) vapor volume and (3) temperature.
According to the subject invention, applicants have succeeded in putting together a thermodynamic model which can be used to select the types of perfume and formulations which should be used in order to maximize this perfume burst or actual headspace (actual concentration of perfume in vapor phase) when a formulation (e.g., personal wash or shampoo formulation) is diluted in use.
More specifically, applicants have defined a perfume burst index which defines compositions which can deliver a perfume burst upon dilution of at least a certain amount relative to undiluted composition; and further allows applicants to define a process for obtaining such compositions.
In general, the burst is achieved by diluting a surfactant system (e.g., an aqueous surfactant system) where upon burst begins upon dilution and maximum burst is obtained upon reaching CMC, therefore, releasing all of the perfume from the surfactant system. Thus, a composition yielding a maximum fragrance burst of 20% means the perfume concentration in the headspace increases by about 20% relative to the undiluted product when the solution is diluted through the CMC. The CMC is the point where perfume-surfactant-water system changes to perfume-water system (i.e., system is too dilute for micelles to form).
A surfactant system is defined as a surfactant and/or surfactant mixtures which may include ingredients selected to manipulate the CMC in a continuous phase. These selected ingredients can include urea; glycerine; C1-C12 straight-chained or branched alcohols or diols; water soluble polymers such as polyvinylpyrolidone, polyvinylalcohol, polyethyleneglycol, polypropyleneglycol; multivalent electrolytes such as magnesium, calcium and aluminum salts; and sugars such as dextrose, glucose, maltose, galactose, sucrose. The continuous phase is typically water, but may also include C1-C8 straight-chained or branched alcohols or diols, glycerine, C1-C8 esters and combinations thereof.
Generally, surfactants which may be used include anionic, nonionic, amphoteric/zwitterionic and cationic surfactants as discussed in more detail below.
In one embodiment, the invention relates to a composition having a fragrance burst, as measured by a xe2x80x9cperfume burst indexxe2x80x9d, of about 20% relative to a composition containing surfactant systems and perfume/fragrance prior to dilution of said product.
More specifically, the invention relates to specific compositions obtained by selecting perfume and/or perfumes and surfactant systems and/or mixtures of surfactant systems and calculating therefrom a perfume burst index (PBI) according to the following formula:   PBI  =            φ      -              1.4        /        CMC              K  
wherein xcfx86=oil/water partition coefficient of selected perfumes or perfume components in a mixture;
CMC=critical micellization concentration of surfactant systems or mixture of surfactant systems (wt./wt.);
K=volatility constant of perfume or perfume components in a mixture from the continuous phase (atmospheres); and
The perfumes and surfactant systems are specifically selected to ensure that the PBI calculated is greater than about 3.
It should be understood that the PBI defines the maximum potential fragrance burst which is achieved at the CMC for the surfactant or surfactant mixture. For example, a relatively low PBI (e.g., about 3) will obtain a xe2x80x9cburstxe2x80x9d of at least 20% as noted. However, if the PBI is higher, much higher fragrance burst can be expected. Thus, for example, a burst of 20% may be achieved upon immediate dilution (assuming high enough PBI) and may continue to 700% or 800% or more at CMC (which as noted is point of maximum potential burst).
As far as applicants are aware, there is no art which specifically discloses that such burst can be obtained with such compositions or which discloses a way of predicting when and under what circumstances such fragrance xe2x80x9cburstxe2x80x9d will occur based on the dilution behavior of a perfume-surfactant-water system. Further no art of which applicants are aware discloses how such compositions are in turn related, for example, to properties of the perfume (e.g., partition coefficient, volatility) as well as to properties of the formulation (e.g., surfactant concentration and surfactant CMC).
The invention relates to surfactant compositions, preferably aqueous surfactant compositions (e.g., bars, personal wash liquids, shampoos) in which perfume and surfactant are selected as to provide a fragrance burst, when diluted, of at least about 20% relative to undiluted product. Compositions must have a perfume burst index, as defined, of about 3.0 or greater, preferably 4.0 or greater.
The invention further relates to a process for selecting such compositions by selecting perfumes and choosing surfactant system or manipulating CMC of surfactant system to ensure the PBI is at least about 3.0.
The invention is based on applicants"" observation that variations in perfume impact (xe2x80x9cburstxe2x80x9d) on dilution are essentially caused by the competition between a decrease in overall fragrance concentration upon dilution; and an increase in fragrance concentration in the continuous phase as the fragrance is released during disassociation of surfactant micelles which occurs during dilution. More specifically, and without wishing to be bound by theory, applicants have observed and shown that only perfumes with relatively large oil/water partition coefficient (very hydrophobic) possess the potential to produce a fragrance burst upon dilution. Other parameters which are important to minimum burst include (1) volatility constant of perfume; (2) surfactant concentration; (3) type of surfactant system; (e.g., CMC) etc.
Specifically, applicants have developed a theoretical mathematical equation based on the various variables noted above. More specifically, they have developed a perfume burst index which both defines compositions having a maximum burst of at least 20% and further provides a process for selecting such compositions based on properties of perfume and surfactant system.
The relationships are defined in more detail below.